1. Field of the Invention
The invention relates to a sensor configuration for determining the position and/or change in position of a measurement object relative to a sensor, such that a magnet is assigned to the measurement object. The invention also relates to a corresponding method.
2. Description of Related Art
Sensor configurations and methods for determining the position and/or change in position are widely used in practice. The positions of pistons, valves, carriages or other movable elements are determined. Areas of application range from household appliances to motor vehicles to precision engineering or industrial manufacturing lines. It is often extremely important for the position or change in position of a measurement object to be detectable with a high sensitivity.
Capacitive or inductive sensors are frequently used, determining the feedback effect of a measurement object on the sensor. Traditional magnetic sensors use the ferromagnetic properties of a measurement object or eddy currents induced in a measurement object. In addition, another class of sensors is known in which a soft magnetic core is influenced by a magnet assigned to the measurement object. Thus, for example, DE 36 10 479 A1 discloses a sensor in which a magnet brings a soft magnetic core to saturation locally and thereby generates a virtual air gap. The position of the air gap can be read out.
Another possibility of measuring the position which also utilizes the effect of a magnet on soft magnetic materials is disclosed in EP 1 721 130 B1 where an alternating field is generated by a conductor loop, inducing a voltage in a sinusoidal conductor structure which acts as a secondary coil. By superimposing a plurality of sinusoidal structures, the direction of movement and position of a measurement object can be determined. However, it has proven to be a disadvantage that the conductor structure has a relatively complex design, must be manufactured with precision, the sensor is designed to be quite broad and a carrier having conductors applied to two sides is always required. This results in relatively high costs in fabrication and an inflexible use.
Another position sensor which operates according to a comparable principle is known from DE 39 14 787 A1. The sensor has a primary coil and at least one secondary coil which are wound around a shared soft magnetic core. A magnet which brings the core locally to saturation as a function of the position of the measurement object is assigned to a measurement object. The resulting virtual air gap acts on the impedance of the coils and their transformation ratio, which can be detected by the measurement technology. For linearization of the characteristic line, the shape of the core is varied in the longitudinal direction. To do so, the core must be machined and the coils must be wound on an oblique core which results in a cost-intensive production of the sensor. Furthermore, the sensor is relatively large which interferes with or completely prevents its use in many areas.
Therefore the object of the present invention is to design a sensor configuration of the type defined in the introduction and to improve upon it, such that the result is a sensor that is more reliable in operation, can be manufactured at a low manufacturing cost and can be used in a flexible manner.